Bus is one of the main transportation in Hong Kong, especially for long-distance travel. I guess this is because you can easily have a seat from starting point until you arrive your destination without any transfer. It provide a chance for passenger to do their own stuff stably. Passengers like to watch TV programme, make-up or even sleep.
Sleeping should be the most private behavior of animal. Since we cannot response to any danger during sleep, we should only sleep inside a safe and private space. However, (Hong Kong) people need to do that on the bus, due to heavy over-time workloads and leaking of personal time.
I tried to record this phenomenon with a pinhole camera. Pinhole camera gives the longest exposure time, in order to capture the sleeping time as long as possible. It also give a dreamy effect to the photo responding to the behavior -- sleeping. Maybe the busy Hong Kong people can only fine their dream during their uncomfortable sleep on the bus.